大亚湾核电站18个月换料堆芯热工水力设计

GNPS 18-Months Fuel Cycles Core Thermal Hydraulic Design

大亚湾核电站从第九循环开始由年换料向18个月换料转换,使得原堆芯热工水力设计不再适用。18个月换料的热工水力设计采用法马通新开发的临界热流密度(CHF)关系式——FC关系式,并用全统计法代替原来的确定论方法确定DNBR设计限值。由于在过渡循环中AFA 2G和AFA 3G燃料组件混装,使混合堆芯的最小DNBR小于均匀堆芯的最小DNBR,本文确定了一个包络的混合堆芯DNBR亏损规律。并在此基础上得到了过渡循环和平衡循环的堆芯物理限值线,以及新的超温ΔT超功率ΔT保护定值。

GNPS begins to implement the 18-month fuel cycles from the initail annual reload at cycle 9, thus the initial core thermal hydraulic design is not valid any more. The new critical heat flux (CHF) correlation, FC, which is developed by Framatome, is used in the design, and the generalized statistical methodology (GSM) instead of the initial deterministic methodology is used to determine the DNBR design limit. As the AFA 2G and AFA 3G are mixed loaded in the transition cycle, it will result that the minimum DNBR in the mixed core is less than that of AFA 3G homogenous core, the envelop mixed core DNBR penalty is given in this paper. Consequently the core physical limit for mixed core and equilibrium cycles, and the new overtemperature ΔT overpower ΔT are determined.